Fuel cell stack

ABSTRACT

A fuel cell stack is disclosed. The fuel cell stack includes a membrane electrode assembly, separation plates on either side of the membrane electrode assembly, current collectors on either side of the separation plates and configured to electrically convey current to an outside circuit, first and second end plates sandwiching the current collectors and configured to apply a connecting pressure, and manifolds formed to pass through the membrane electrode assembly, at least one of the separation plates, at least one of the current collectors, and at least one of the end plates, the manifolds configured to conduct reaction gas, and cutoff blocks inserted into a portion forming manifolds of the end plates to separate the current collectors and the end plates on a passage in which the reaction gas is circulated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of Korean PatentApplication No. 10-2011-0097747 filed in the Korean IntellectualProperty Office on Sep. 27, 2011, the entire contents of which areincorporated herein by reference.

BACKGROUND

1. Field of the Disclosure

The described technology relates generally to a fuel cell, and moreparticularly, to a fuel cell stack including a manifold circulating areaction gas supplied to the fuel cell.

2. Description of the Related Technology

In general, a fuel cell is an apparatus for electrochemically generatingelectricity using a hydrogen gas and an oxygen gas. More specifically,the fuel cell converts a continuously supplied fuel (hydrogen) and air(oxygen) into electrical energy and heat by an electrochemical reaction.Electric power is generated using an oxidation reaction in an anode anda reduction reaction in a cathode.

Currently, the fuel cell is variously researched and used as analternative power source and representatively, may be a polymer typefuel cell. The polymer type fuel cell has various advantages of havinghigh output density and high energy conversion efficiency, being able tooperate even at low temperatures of 80° C. or less, and being able todown-sized and sealed. As a result, the fuel cell is used as thealternative power source in various fields such as non-pollutingvehicles, home electric generator systems, mobile communicationequipment, military equipment, medical equipment, and the like.

In the polymer type fuel cell, the output of the electrical energydepends on moving a hydrogen ion through a polymer film. In order thatthe hydrogen ion easily moves through the polymer film, the polymer filmshould be hydrated with appropriate water. Accordingly, to hydrate thepolymer film, the reaction gas inputted in to the anode and the cathodeof the fuel cell is generally humidified. Therefore, a relatively largeamount of water is contained in the reaction gas circulating the fuelcell.

The electricity and heat reaction products due to the electrochemicalreaction are generated in the fuel cell such that a cooling is required.Accordingly, cooling water may be circulated in the fuel cell. Thereaction gas and the cooling water flow in the fuel cell through themanifold formed in the fuel cell via an end plate and a currentcollector. In this process, when a metallic current collector is exposedto the water, galvanic corrosion may occur in the current collector.

The above information is only for enhancement of understanding of thebackground of the described technology and therefore it may containinformation that does not form the prior art that is already known inthis country to a person of ordinary skill in the art.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

In a first aspect, a fuel cell stack having advantages of a structurecapable of preventing a current collector from being corroded by areaction gas moving through a manifold is provided.

In another aspect, a fuel cell stack is provided. The fuel cell stackincludes, for example, a membrane electrode assembly (“MEA”), separationplates sandwiching and contacting both sides of the MEA, currentcollectors sandwiching both sides of the separation plates, the currentcollectors configured to conduct electrical energy to an outsidecircuit, first and second end plates sandwiching opposite sides of thecurrent collectors and configured to apply a connecting pressure to thecurrent collectors, manifolds formed to pass through the MEA, at leastone of the separation plates, at least one of the current collectors,and at least one of the end plates, the manifolds configured to fluidlycommunicate reaction gas, and cutoff blocks inserted into a portion ofthe end plates forming the manifolds, the cutoff blocks configured toelectrically separate the current collectors and the end plates from apassage in which the reaction gas is circulated.

In some embodiments, the current collectors include a cathode currentcollector adjacent to the first end plate and an anode current collectoradjacent to the second end plate. In some embodiments, the cutoff blocksinclude a first block inserted into the portion forming the manifold ofthe first end plate and protruding to a portion forming the manifold ofthe cathode current collector configured to block the contact betweenthe reaction gas and the cathode current collector and a second blockinserted into a portion forming the manifold of the anode currentcollector adjacent to the second end plate configured to block contactbetween the reaction gas and the anode current collector. In someembodiments, the first block is formed of a non-metallic material. Insome embodiments, the first block is formed in a polyhedral or cylindershape with a through-hole connection with the manifold. In someembodiments, the first block is formed so that a portion protruding tothe cathode current collector side is the same as a thickness of thecathode current collector. In some embodiments, the first block isformed of the non-metallic material including synthetic resins orpolytetrafluoroethylene (PTFE). In some embodiments, in the first endplate, an insertion part into which the first block is inserted isformed at the portion with the manifold and a gasket is installedbetween the insertion part and the first block. In some embodiments, thesecond block contacts the surface of the second end plate. In someembodiments, the second block is formed of a non-metallic material. Insome embodiments, the second block is formed of the non-metallicmaterial including synthetic resins or polytetrafluoroethylene (PTFE).In some embodiments, the current collectors include a cathode currentcollector adjacent to the first end plate and an anode current collectoradjacent to the second end plate. In some embodiments, the cutoff blocksinclude a first block inserted into a portion forming the manifold ofthe first end plate configured to separate the cathode current collectorfrom the first end plate and a second block inserted into a portionforming the manifold of the anode current collector adjacent to thesecond end plate configured to block contact between the reaction gasand the anode current collector. In some embodiments, the first blockcontacts the surface of the cathode current collector.

In another aspect, a cutoff block in a fuel cell stack is provided. Thecutoff block is configured to block contact between a current collectorand reaction gas in a manifold to prevent the current collector frombeing corroded due to the water of the reaction gas. In someembodiments, durability of the fuel cell stack is thus improved.

In another aspect, contact between different metals of a currentcollector and an end plate is blocked by providing a cutoff block in themanifold to prevent the current collector from corrosion. In someembodiments, durability of the fuel cell stack is thus improved.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, together with the specification, illustrateexemplary embodiments of the present disclosure, and, together with thedescription, serve to explain the principles of the present disclosure.

FIG. 1 is a perspective view schematically showing a fuel cell stackaccording to a first exemplary embodiment of the present disclosure.

FIG. 2 is a side view of the fuel cell stack of FIG. 1 viewed from theside.

FIG. 3 is an exploded perspective view of a fuel cell stack according tothe first exemplary embodiment of the present disclosure.

FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 1.

FIG. 5 is a cross-sectional view schematically showing a state in whicha first block is installed in a fuel cell stack according to a secondexemplary embodiment of the present disclosure.

FIG. 6 is a diagram schematically showing a state in which a first blockis inserted into a first end plate according to the second exemplaryembodiment of the present disclosure.

FIG. 7 is a side view schematically showing a fuel cell stack accordingto a third exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTIVE EMBODIMENTS

Hereinafter, a fuel cell stack according to exemplary embodiments of thepresent disclosure will be described with reference to the accompanyingdrawings. As those skilled in the art would realize, the describedembodiments may be modified in various different ways, all withoutdeparting from the spirit or scope of the present disclosure. On thecontrary, exemplary embodiments introduced herein are provided to makedisclosed contents thorough and complete and sufficient transfer thespirit of the present disclosure to those skilled in the art.

FIG. 1 is a perspective view schematically showing a fuel cell stackaccording to a first exemplary embodiment of the present disclosure,FIG. 2 is a side view of the fuel cell stack of FIG. 1 viewed from theside, and FIG. 3 is an exploded perspective view of a fuel cell stackaccording to the first exemplary embodiment of the present disclosure.As shown in FIGS. 1 to 3, a fuel cell stack 100 according to the firstexemplary embodiment includes a membrane electrode assembly (MEA) 10,separation plates 20 (21 and 23) contacting both sides of the membraneelectrode assembly, current collectors 30 (31 and 33) stacked at bothsides of the separation plates 20 (21 and 23) and configured to draw outelectrical energy to the outside, end plates 40 (41 and 43) connected atthe sides of the current collectors 30 (31 and 33) while applying aconnecting pressure, and cutoff blocks 60 (61 and 63) inserted intomanifolds 50 (101, 211, 231, 311, 331, and 413) where the reaction gasmoves to block a contact between the reaction gas and the currentcollectors 30 (31 and 33).

The fuel cell stack 100 to be described below means a constituentelement configured for generating the electrical energy byelectrochemically reacting with hydrogen and oxygen. In the exemplaryembodiment, the fuel cell stack 100 exemplifies a unit cell statecombined by the membrane electrode assembly 10, a single electricitygenerator configured by the separation plates 20 (21 and 23), and thecurrent collectors (30; 31, 33). However, the exemplary embodiment isnot limited thereto and may also be applied to a state in which aplurality of unit cells is continuously stacked.

The membrane electrode assembly 10 includes a polymer electrolytemembrane configured to selectively pass hydrogen ions. An anode and acathode are connected at both surfaces of the polymer electrolytemembrane. In addition, a fluid distributing layer is configured totransfer the reaction gas used in the electrochemical reaction to anelectrode and discharge a product due to the electrochemical reaction.More detailed configuration and operation of the membrane electrodeassembly 10 are known and the detailed description is omitted below. Theseparation plates 20 (21 and 23) are stacked at the side of the membraneelectrode assembly 10.

The separation plates 20 (21 and 23) are stacked at the side of themembrane electrode assembly 10 and configured to structurally supportthe fuel cell stack 100. The separation plates 20 (21 and 23) include acathode separation plate 21 stacked at one side of the membraneelectrode assembly 10 and an anode separation plate 23 stacked at theother side of the membrane electrode assembly 10. The separation plates20 (21 and 23) are also configured to supply the reaction gas or coolingwater from the outside and also are configured to discharge the productsuch as water generated after the electrochemical reaction of thereaction gas and the like to the outside. The reaction gas may beapplied by a fuel gas, an oxidant gas, or the like and supplied throughthe manifold 50.

The cathode separation plate 21 includes an oxidant gas channel formedat one side facing the membrane electrode assembly 10 and may beconfigured such that the oxidant gas containing oxygen flows into theoxidant gas channel through the manifold 50.

The anode separation plate 23 includes a fuel gas channel formed at oneside facing the membrane electrode assembly 10 and may be configuredsuch that the fuel gas containing hydrogen flows into the fuel gaschannel through the manifold 50. The oxidant gas channel and the fuelgas channel may be implemented in various forms and the detailed drawingfor the channels is omitted.

A gasket 232 may be configured to prevent the reaction gas from leakingin the manifold 311 and may be fabricated by a material includingsilicon-based, fluorine-based, olefin-based, and ethylene propylenedienemonomer (EPDM) rubbers, a glass fiber-reinforced silicon sheet, or ateflon sheet. The gasket 232 may be formed of a corrosion resistantmaterial such that it is not easily corroded. The gasket 232 may also bepositioned relatively close to another constituent element so that thereaction gas does not leak.

The manifold 50 may be formed with the membrane electrode assembly 10,the cathode separation plate 21, and the anode separation plate 23 in astack. In more detail, the manifold 50 may be formed as one passageconfigured to supply the reaction gas by stacking and connecting amanifold 101 of the membrane electrode assembly 10, a manifold 211 ofthe cathode separation plate 21, and a manifold 231 of the anodeseparation plate 23. Here, the manifold 101 of the membrane electrodeassembly 10, the manifold 211 of the cathode separation plate 21, andthe manifold 231 of the anode separation plate 23 may be disposed at anouter edge area, not a reaction gas area in which the electrochemicalreaction with hydrogen and oxygen is caused.

The current collectors 30 (31 and 33) are stacked at the sides of thecathode separation plate 21 and the anode separation plate 23. Thecurrent collectors 30 (31 and 33) includes a cathode current collector31 stacked at one side of the cathode separation plate 21 and an anodecurrent collector 33 stacked at one side of the anode separation plate23. In the cathode current collector 31 and the anode current collector33, the manifolds 311 and 331 may be formed and configured to supply thereaction gas in a direction of the membrane electrode assembly 10.

A drawn tap 35 is formed at the current collectors 30 (31 and 33). Anexternal wire may be electrically connected to the drawn tap 35 suchthat the electrical energy may be drawn out to the outside. The endplates 40 (41 and 43) are installed at each side of the cathode currentcollector 31 and the anode current collector 33. The end plates 40 (41and 43) include a first end plate 41 connected at the side of thecathode current collector 31 while configured to apply a connectionpressure and a second end plate 43 connected at the side of the anodecurrent collector 33 while configured to apply a connection pressure.The end plates 40 (41 and 43) may secure and connect the membraneelectrode assembly 10, the cathode current collector 31, and the anodecurrent collector 33 to each other with a predetermined connectionpressure while protecting the membrane electrode assembly 10, thecathode current collector 31, and the anode current collector 33.

Meanwhile, the cutoff blocks 60 (61 and 63) are located and configuredto block a contact between the reaction gas and the current collectors30 (31 and 33). The cutoff blocks 60 (61 and 63) are installed in themanifold 50. The cutoff blocks 60 (61 and 63) are installed andconfigured to prevent the corrosion generated when the reaction gascontaining water is contacted with the current collectors 30 (31 and 33)made of a metal material.

FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 1. Asshown in FIG. 4, the cutoff blocks 60 (61 and 63) includes a first block61 inserted into the manifold to block the contact between the reactiongas and the cathode current collector 31 and a second block 63 insertedinto the manifold 50 configured to block the contact between thereaction gas and the anode current collector 33. A part of the side ofthe first block 61 is inserted and fixed in the end plate 40 in themanifold 50. In more detail, the first block 61 is formed in a column orpolyhedral shape corresponding to a shape of the manifold 50 to beinserted and fixed in the end plate 41.

To install the first block 61, an insertion part 411 is formed at thefirst end plate 41. The insertion part 411 is formed at the manifold 413formed at the first end plate 41. The insertion part 411 has a sizelarger than a diameter of the manifold 413 formed at the first end plate41 to form a space in which the first block 61 may be seated. In thestate where the first block 61 is inserted into the first end plate 41,a part of the cathode current collector 31 side protrudes to the outsideof the surface of the first end plate 41. A protruding height of thefirst block 61 may protrude in a height corresponding to a thickness ofthe cathode current collector 31. This is to prevent the cathode currentcollector 31 from being exposed to the manifold 50 by the protrudingportion of the first block 61. Accordingly, the reaction gas containingwater is blocked from being contacted with the cathode current collector31, such that it is possible to prevent the cathode current collector 31from being corroded.

The first block 61 may be made of a non-metallic material to preventcorrosion due to the contact with the reaction gas containing water.Synthetic resins, polytetrafluoroethylene (PTFE), or the like may beselected as the non-metallic material, but it is not limited thereto andthe first block 61 may be made of any non-metallic material that doesnot corrode when contacted with water.

Meanwhile, the gasket 65 may be installed between the first block 61 andthe insertion part 411. The gasket 65 may be configured to prevent thereaction gas from being leaked in the manifold 50 and may be fabricatedby any material selected from a material including silicon-based,fluorine-based, olefin-based, and ethylene propylenediene monomer (EPDM)rubbers, a glass fiber-reinforced silicon sheet, and/or a PTFE sheet.The gasket 65 may be formed and configured to resist corrosion and maybe formed with another constituent element so that the reaction gas doesnot leak.

The second block 63 is inserted into the manifold 331 of the anodecurrent collector 33. The second block 63 may be installed in a plateshape having a thickness corresponding to the thickness of the anodecurrent collector 33. As described above, the second block 63 isinserted and fixed into the manifold 331 of the anode current collector33 such that the reaction gas moving in the manifold 50 can be blockedfrom being contacted with the anode current collector 33. The secondblock 63 is configured to block the reaction gas from contacting theanode current collector 33 and configured to prevent the corrosion. Thesecond block 63 may be formed of a non-metallic material such assynthetic resin, polytetrafluoroethylene (PTFE), or the like havingexcellent corrosion resistance.

As described above, during operation of the fuel cell, the reaction gasmoving in the manifold does not directly contact the current collectors30 (31 and 33). Thus, the current collectors 30 (31 and 33) may beprevented from being corroded by the water included in the reaction gas.

FIG. 5 is a cross-sectional view schematically showing a state in whicha first block is installed in a fuel cell stack 200 according to asecond exemplary embodiment of the present disclosure and FIG. 6 is adiagram schematically showing a state in which a first block is insertedinto a first end plate according to the second exemplary embodiment. Thesame reference numerals as FIGS. 1 to 4 mean the same members having thesame function. Hereinafter, the detailed description of the samereference numerals is omitted.

As shown in FIGS. 5 and 6, a fuel cell stack 200 according to the secondexemplary embodiment includes a first block 161 inserted into themanifold 50 to separate the exposed portion to the manifold 311 of thecathode current collector 131 from the first end plate 41 and a secondblock 63 inserted into the manifold 50 to block the contact between theanode current collector 33 and the reaction gas. The first block 161 maybe formed in a polyhedral or cylinder shape to be inserted into theinsertion part 411 formed in the first end plate 41. In the first block161, a protruding portion to the cathode current collector 31 side ofthe first end plate 41 is not provided while being inserted into theinsertion part 411. In this case, the cathode current collector 131further extends to a portion in which the first block 61 is installedsuch that a part of the cathode current collector 131 may be exposed inthe manifold 50. The first block 161 may be made of a non-metallicmaterial such as synthetic resins, polytetrafluoroethylene (PTFE), orthe like. The first block 161 is made of the non-metallic material tomaintain the first end plate 41 and the cathode current collector 131 tobe separated from each other with a predetermined distance in themanifold 50. That is, in the cathode current collector 131 and the firstend plate 41 which are made of the metallic material, the exposedportions to the manifold 50 are separated from each other by the firstblock 161. Accordingly, it is possible to prevent the corrosion frombeing progressed by the electrical conduction between different metalsin the manifold 50.

FIG. 7 is a side view schematically showing a fuel cell stack accordingto a third exemplary embodiment of the present disclosure. The samereference numerals as FIGS. 1 to 6 mean the same members having the samefunction. Hereinafter, the detailed description of the same referencenumerals is omitted. As shown in FIG. 7, a fuel cell stack 300 accordingto the third exemplary embodiment has a structure including a pluralityof electricity generators. That is, the plurality of electricitygenerators including a membrane electrode assembly, a cathode separationplate 21 stacked at one side of the membrane electrode assembly, and ananode separation plate 23 stacked at the other side of the membraneelectrode assembly may be stacked. By the above configuration, muchhigher voltage may be generated in the fuel cell stack 300 duringoperation of the fuel cell.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A fuel cell stack, comprising: a membraneelectrode assembly (“MEA”); separation plates sandwiching and contactingboth sides of the MEA; current collectors sandwiching both sides of theseparation plates, the current collectors configured to conductelectrical energy to an outside circuit; first and second end platessandwiching opposite sides of the current collectors and configured toapply a connecting pressure to the current collectors; manifolds formedto pass through the MEA, at least one of the separation plates, at leastone of the current collectors, and at least one of the end plates, themanifolds configured to fluidly communicate reaction gas; and cutoffblocks inserted into a portion of the end plates forming the manifolds,the cutoff blocks configured to electrically separate the currentcollectors and the end plates from a passage in which the reaction gasis circulated.
 2. The fuel cell stack of claim 1, wherein the currentcollectors include a cathode current collector adjacent to the first endplate and an anode current collector adjacent to the second end plate,and wherein the cutoff blocks include a first block inserted into theportion forming the manifold of the first end plate and protruding to aportion forming the manifold of the cathode current collector configuredto block the contact between the reaction gas and the cathode currentcollector and a second block inserted into a portion forming themanifold of the anode current collector adjacent to the second end plateconfigured to block contact between the reaction gas and the anodecurrent collector.
 3. The fuel cell stack of claim 2, wherein the firstblock is formed of a non-metallic material.
 4. The fuel cell stack ofclaim 2, wherein the first block is formed in a polyhedral or cylindershape with a through-hole connection with the manifold.
 5. The fuel cellstack of claim 4, wherein the first block is formed of a non-metallicmaterial.
 6. The fuel cell stack of claim 2, wherein the first block isformed so that a portion protruding to the cathode current collectorside is the same as a thickness of the cathode current collector.
 7. Thefuel cell stack of any one of claim 6, wherein the first block is formedof a non-metallic material.
 8. The fuel cell stack of claim 7, whereinthe first block is formed of the non-metallic material includingsynthetic resins or polytetrafluoroethylene (PTFE).
 9. The fuel cellstack of claim 2, wherein in the first end plate, an insertion part intowhich the first block is inserted is formed at the portion with themanifold and a gasket is installed between the insertion part and thefirst block.
 10. The fuel cell stack of claim 2, wherein the secondblock contacts the surface of the second end plate.
 11. The fuel cellstack of claim 10, wherein the second block is formed of a non-metallicmaterial.
 12. The fuel cell stack of claim 11, wherein the second blockis formed of the non-metallic material including synthetic resins orpolytetrafluoroethylene (PTFE).
 13. The fuel cell stack of claim 1,wherein the current collectors include a cathode current collectoradjacent to the first end plate and an anode current collector adjacentto the second end plate, and wherein the cutoff blocks include a firstblock inserted into a portion forming the manifold of the first endplate configured to separate the cathode current collector from thefirst end plate and a second block inserted into a portion forming themanifold of the anode current collector adjacent to the second end plateconfigured to block contact between the reaction gas and the anodecurrent collector.
 14. The fuel cell stack of claim 13, wherein thefirst block contacts the surface of the cathode current collector.